features requset: support garmin-China(garmin.cn) and download activities after a certain time.

[yihong0618]

Hi,
thank you for your great job for this repo.

1. Beacause I am working on running_page to support garminconnect
   I run in China, and there's a different api for Chinese runners, like https://connect.garmin.cn/modern/
   except for the cn instead of com, others are the same.
   like below
   
   can we offer a parameter like cn for Chinese runners?
   something like this

client = Garmin(YOUR_EMAIL, YOUR_PASSWORD, is_cn=True)

2. because I download every day gpx using GitHub Actions so if we can only download the activities after a certain time will be wonderful. like my runtastic repo do.

Can I take a pr for these features?

[cyberjunky]

@yihong0618 If you want to contribute with a PR, please do so! If not let me know, and I can implement it, when I find some time.

[yihong0618]

@cyberjunky
Got it, will do this in this weekend thank you~

[yihong0618]

@cyberjunky
This PR support connect.garmin.cn

[yihong0618]

I think there is no need to support after a certain
Because we hava get_activities_by_date now.

So this issue can be closed

[cyberjunky]

@yihong0618 I see you have used my code in your project and made it async, nice. Wanted to do that too.